Large, multi-satellite constellation systems are expensive to build and place into orbit. Because of the expense, it is desirable to fully utilize the space-based resources to provide revenue producing communication services to users and to minimize the amount of resources that are not providing services to users.
A "satellite" is defined herein to mean a man-made object or vehicle intended to orbit Earth and includes both geostationary and non-geostationary satellites. A "constellation" is defined herein to mean an ensemble of satellites arranged in orbits for providing specified coverage of a portion or all portions of the Earth. A constellation typically includes multiple rings (or planes) of satellites and can have equal numbers of satellites in each plane, although this is not essential. A constellation could include geostationary or non-geostationary satellites, or a combination of both.
A "call" is defined herein as a limited data transfer session having a beginning and an end between two communication units. A call could be, for example, a phone call, a facsimile transmission, or an electronic file transfer between two communication units. A "communication unit" could be, for example, a wireless or wireline telephony device, a facsimile machine, or a computer or other data terminal. In prior-art systems, each time a call is setup between communication units, a call setup procedure is performed during which a communication path is established between the units. When the data transfer is complete, the communication path is relinquished, or torn down.
Call setup procedures utilize resources in the system. Each call set-up procedure involves an exchange of messages between the initiating communication unit and the system, and between the system and a termination communication unit. These call set-up messages generate communication traffic which is non-revenue bearing in nature. A certain portion of system capacity must be allocated for these non-revenue bearing processes.
In prior art systems, communication resources are put into service based on predicted utilization from a number of users located around the world. Because the predictions, by their nature, are somewhat inaccurate to describe actual demand, some system resources are under utilized when system resources are allocated according to the predictions. Allocating system resources based on predictions and in order to respond to each call request can be costly to the system and can result in a large amount resources being consumed by non-revenue bearing information. In addition, performing call setup procedures between communication units for each data transfer session increases the time required to communicate the information.
What are needed are a method and apparatus for more efficiently using system resources by allocating system resources to users on a longer-duration basis.